Electric furnace ventilation and gas cooling cleaning system

ABSTRACT

An electric furnace ventilation and gas cooling and cleaning system including a duct system for combusting, cooling and vertically venting dry waste gases from the furnace. There is a lower pivoted cooling duct and an upper fixed cooling duct horizontally and vertically offset to the furnace and the lower pivoted duct. A horizontally disposed duct interconnects the upper fixed duct and lower pivoted duct. A vertically movable duct is located between the furnace and the vertically pivoted duct and the rate of air intake to the vertically movable duct is varied at each end thereof. Each of the ducts is formed of four water-cooled panels joined together at their edges.

United States Patent FOREIGN PATENTS Priniary Examiner-Edward G. Favors Anorney-Frease and Bishop ABSTRACT: An electric furnace ventilation and gas cooling and cleaning system including a duct system for combusting, cooling and vertically venting dry waste gases from the furnaceaThere is a lower pivoted cooling duct and an upper fixed cooling duct horizontally and vertically offset to the furnace and the lower pivoted duct. A horizontally disposed duct interconnects the upper fixed duct and lower pivoted duct. A vertically movable duct is located between the furnace and the vertically pivoted duct and the rate of air intake to the vertically movable duct is varied at each end thereof. Each of the ducts is formed of four water-cooled panels joined together at their edges.

- ELECTRIC FURNACE VENTILATION AND GAS COOLING'CLEANING SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to electric furnaces for steel refining purposes and more particularly to a new and unique arrangement of water-cooled ducts for carrying uncombusted waste gases, dust and other exhaust products sway from the furnace.

2. Description of the Prior Art 'Although many attempts have been made to carry uncombusted waste gases; dust and other exhaust products away from an electric steel refining furnace, no one, to applicants knowledge, has suggested an arrangementof pivoted, fixed horizontally disposed and vertically movable ducts as provided in applicants invention.

The nearest prior art of which applicants are aware is U.S. Pat. No. 3,453,369'issued July I, 1969, but-this patent does not disclose applicants combination of pivoted and fixed cooling ducts horizontally and vertically offset, a horizontally disposed duct interconnecting the upper fixed and lower pivoted ducts and the vertically movable duct between the furnace and the vertically pivoted duct.

SUMMARY OF THE INVENTION Modern steel making and/or refining furnaces include open h earths, basic oxygen and electric furnaces, all of which can, and usually do, expedite the length of time of refinement of the charge of molten metal and scrap, in varying amounts, de-

pending upon the availability of hot (blast furnace) metal by utilizing oxygen-blowing lances. Steel making plants of a tonna'ge capacity insufficient to involve readily available hot metal may justify large capacity electric furnaces which melt the scrap steel by means of conventional electrodes when aided by the oxygen-bearing lances.

In such type of furnace, it is necessary to more closely con trol the rate of removal of the uncombusted dirt-bearing gases than similar gas generated within open hearths and basic oxygen furnaces, primarily because of the manner and means by which they are charged with hot metal, scrap metal and addition agents. Thus the rate of removal of gases absolutely necessitates a system or arrangement of removal which does not interfere with the charging which must be directly over an electric furnace.

The reaction of oxygen lances on steel being melted by electrodes results in waste gases within the furnace shell, having perhaps as high as 3,000" F. in temperature and having uncombusted poisonous carbon monoxide (CO) gas in high but varying amounts depending on furnace activity (rate of oxygen lance flow) and ventilation requirements. Air ventilation to, and sometimes within, the furnace must be initiated to aid in controlling the rate of gas and dust removal therefrom.

Too limited an amount being exhausted involves leakage into the atmosphere surrounding the furnace, thereby creating a health and working hazard. Too great an amount being exhausted deprives the electrodes of adequate vacuum protection, thus speeding up the combustion of the electrodes and taking away a gas protecting layer from below the refractorylined removable arch or furnace cover.

It is, therefore, a primary object of this invention to provide a waste gas cooling system so constructed and arranged as to permit horiz'ontalto-vertical flow of the waste gases from atop the furnace without interfering with the topside charging of the furnace via the conventional overhead devices such as overhead electric traveling cranes or the like.

Another object of the invention is to provide a water-cooled duct system wherein the hot (3,000 F.) gases are cooled and vertically discharged within a short space interval into a duct that does not need to be internally water separated as heretofore considered necessary. The elimination of such separating of the waste gases minimizes corrosive effect and thus corrosion resis tant linings, as previously necessary in noncooled ducts which normally exist beyond the cooled ducts, are not necessary.

A further object of the invention is the provision of a duct system that permits substantially complete combustion of the high amount of combustible (carbon monoxide) gases within a short time in horizontal-to-vertical interconnected ducts which permits discharge of sufficiently cooled and combusted gases, thus minimizing pollution and excessive cooling facilities.

A still further object of the invention is the use of interchangeable cooling panels having water interconnections of simple construction and with a maximum of cooling effect.

It is also an object of the invention that this unique duct arrangement permits its being pivoted, thus permitting adjustable combustion air infiltration and adequate lateral roof movement clearance.

Finally, it is an object of the invention to provide a cooling and ventilation system wherein pivoted vertical ducts are offset to a subsequently higher fixed duct,thereby permitting upward exhaust without impeding top charging of the furnace.

These and other objects apparent from the drawings and following description, may be attained, the above-described difficulties overcome and the advantages and results obtained, by the apparatus, construction, arrangement and combinations, subcombinations and parts which comprise the present invention, a preferred embodiment of which, illustrative of the best mode in which applicants have contemplated applying the principle, being set forth in detail in the following description and illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation of equal but opposed duct systems connected to a pair of equal but opposite electric furnaces;

FIG. 2 is a side elevation of the duct system taken as on line 2-2, FIG. 1;

FIG. 3 is a detached perspective view of one complete duct system wherein the upper fixed vertical duct in relation to the offset lower pivoted duct is more clearly shown;

F IG. 4 is a top plan view of the pair of duct systems as viewed on the line 4--4, FIG. 1;

FIG. 5 is a transverse sectional view through one of the ducts as on the line 5-5, FIG. 1; and

FIG. 6 is a detached perspective view of a typical watercooled panel, from which the several ducts are formed, broken in section for purpose of illustration.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now more particularly to the embodiment illustrated in the drawings, in which similar numerals refer to similar parts throughout, a pair of electric furnaces for steel refining purposes or the like is indicated at I having arch covers 2.

An elbow or snorkel indicated generally at 3 in the form of a four-sided water-cooled duct is so located that its entry end overhangs an opening in the arch cover 2. As best shown in FIG. 1, the elbow 3 is attached to horizontally pivoted roof support beams 4 which are pivoted about a vertical post 5. The attachment of the pivoted roof support beams 4 to the elbow 3 is effected by means of a pair of trunnions 6 and 7 which traverse the elbow 3 in a spaced parallel arrangement. The longer trunnion 6 rests at both ends in saddles 8 supported upon the roof beams 4. The shorter trunnion 7 rests at each end in saddles 9 also supported by the roof beams 4. The trunnion 7 is tubular and supplies cooling media (water) to the four internally cooled panels 10 which form the elbow 3. The cooling water enters one panel from one end of the trunnion 7 and the panels are connected together by interconnecting tubes 11.

Each of the ducts to be later described, as well as the elbow 3, is formed of four hollow water-cooled panels made in accordance with the disclosure in Reighart US. 1 Pat. No. 3,445,l01, issued May 20, 1969, and may be constructed as shown in detail in FIG. 6.

The uncombusted gases exit from furnaces 1 into and through the elbows 3 at which time such hot gases (3,000 F.) are not only considerably and rapidly cooled but substantially all (90 percent) of the gas is combusted. Such combustion is aided by air infiltration between and spaced-apart furnace cover 2 and entry end 12 of elbow 3. The degree of air infiltration between elbow 3 and arch roof cover 2 can be varied by raising and/or lowering the elbow via its support trunnions 6 and 7.

A noncooled, dry flange 13 is attached to the outer periphery of the exit end 14 of each elbow 3, the outermost dimensions of which are large enough to cover the opening or entry 15 in the adjacent interconnecting vertically disposed pivoted water-cooled duct 16. When the furnace is tilted (:tS" the gases exiting from each elbow 3 are conducted to the corresponding pivoted vertical duct 16 with substantially no leakage. Thus, complete draft is maintained.

The vertical duct 16 is preferably pivoted to permit lateral movement of the furnace roof 2 and also to adjust, if desired, the volume of air to infilter into the gases at this point in the system to permit further combustion of any remaining gases. This pivoting action essentially produces a lateral movement to the lower end of duct 16.

The vertical pivoted duct 16 is also a substantially foursided structure made up of a plurality of preferably interchangeable internal (water) cooled panels 17. The cooling water courses from panel to panel in any desired flow pattern by means of flexible interconnection 18 similar to those previously described for the elbow 3. This pivoted duct 16 is pivoted as at 19 in pivot bearings and supports 20.

The combusted and partially cooled gases thus pass from the pivoted duct 16 into and through a horizontally disposed water-cooled duct 21 referred to as a transition duct since it connects with another water-cooled vertical duct 22 offset to the vertical pivoted duct 16.

The horizontal or transition duct 21, between the offset lower pivoted duct 16 and the fixed vertical duct 22, is essen tial to the success of this duct system when considered in combination with an electric furnace which must, of necessity, be charged topside when its arch cover 2 is horizontally swung away therefrom. Charging furnaces of thistype can be economically accomplished by overhead traveling cranes. The absence of ducts for waste gases readily makes this possible.

Thus, the primary object of this duct system provides such accomplishment. The vertical duct 16 being pivoted, the upper end thereof cannot fixedly be secured to the horizontal or transition duct 21, but no interconnecting flange is necessary between these two ducts since movement of the upper end of the pivoted duct 16 is relatively slight as compared to the lower end thereof. The combined overall thickness of the water-cooled panels of both the pivoted vertical duct 16 and the horizontal or transition duct 21 is sufficient to serve as a flange.

The exit end 23 of the horizontal or transition duct 21 carries the combusted waste gases, now still further cooled, to and into the final vertical fixed water-cooled duct 22 which is fixed thereto. As shown in the drawings, this final vertical duct 22 is horizontally offset to its corresponding vertical duct 16,

to permit continuance of the upward flow of waste gases and to bypass essentially auxiliary furnace equipment which may exist incidental to the previously mentioned overhead furnace charging equipment.

At this point it may be described that such offset vertical and horizontal transition ducts provide angular gas flow essentially and emphatically at both ends of the pivoted duct 16, thereby creating a natural tendency for dust particles to drop out of the cooled, combusted steam of waste gases. The dust particles can then be collected and periodically removed in any conventional manner from a dust bin 24 removably connected' to the lower end of the pivoted duct 16. The watercooled panels of the elbow 3, vertical pivoted duct 16, horizontal transition duct 21 and vertical fixed duct 22 may all be constructed and arranged in accordance with Reighart U.S.

Pat. No. 3,445,10l issued Ma 20, 1969. It should be understood that because structura beams OET cranes and other equipment ancillary to electric furnaces confine available space for this duct system, the water connections to such panels may have to be sometimes modified. This duct system is novel by utilizing sufficient drastic cooling of the combusted waste gases to eliminate (water) spray cooling heretofore considered necessary.

This also eliminates the creation of larger volumes of (wet) gases which are generally of a corrosive nature. Any further duct beyond that shown and described as a novel duct system may be unlined and dry as only dry noncorrosive gases contact their inner surfaces.

In the foregoing description certain terms have been used for brevity, clearness and understanding, but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such words are used for descriptive purposes herein and are intended to be broadly construed.

Moreover, the embodiment of the improved construction illustrated and described herein is by way of example, and the scope of the present invention is not limited to the exact details of construction.

Having now described the invention or discovery, the construction, the operation, and use of the preferred embodiment thereof, and the advantageous, new and useful results obtained thereby; the new and useful construction, and reasonable mechanical equivalents thereof obvious to those skilled in the art, are set forth in the disclosure.

We claim:

1. In combination with an electric metal refining furnace having an outlet aperture in its upper portion, a duct system for combusting, cooling and vertically venting dry waste gases from said furnace through said aperture, said duct system comprising a lower laterally shiftable cooling duct pivoted about a horizontal axis, a vertically movable duct between said furnace aperture and said laterally shiftable duct, an upper fixed cooling duct, said fixed duct being both horizontally and vertically offset from both said furnace and said lower laterally shiftable duct, and a horizontally disposed duct interconnecting said upper fixed duct and said lower laterally shiftable duct.

2. In combination with an electric metal refining furnace, a duct system as defined in claim 1, having a mechanical mearis on at least one end of said vertically movable duct to vary the rate of air intake thereinto.

3. In combination with an electric metal refining furnace, a duct system as defined in claim 1, in which the walls of all of said ducts are hollow water cooled panels. 

1. In combination with an electric metal refining furnace having an outlet aperture in its upper portion, a duct system for combusting, cooling and vertically venting dry waste gases from said furnace through said aperture, said duct system comprising a lower laterally shiftable cooling duct pivoted about a horizontal axis, a vertically movable duct between said furnace aperture and said laterally shiftable duct, an upper fixed cooling duct, said fixed duct being both horizontally and vertically offset from both said furnace and said lower laterally shiftable duct, and a horizontally disposed duct interconnecting said upper fixed duct and said lower laterally shiftable duct.
 2. In combination with an electric metal refining furnace, a duct system as defined in claim 1, having a mechanical means on at least one end of said vertically movable duct to vary the rate of air intake thereinto.
 3. In combination with an electric metal refining furnace, a duct system as defined in claim 1, in which the walls of all of said ducts are hollow water cooled panels. 